Autoelectronic device



March 23 1926. 1,578,045

J. E. LILIENFELD AUTOELECTRONIC DEVICE Filed Jan. 28, 1922 c/u/z'usEdyarLilz'enfeZa INVENTOR BY Q v 2 ATTORNEY Patented Mar. 23, 1926.

UNITED STATES PATENT OFFICE.

JULIUS EDGAR LILIENFELD, OF WATERBURY, CONNECTICUT, ASSIGNOR OF ONE-HALFT0 WILLIAM H. BRISTOL, OF WATEBBURY, CONNECTICUT.

AUTOELEC'IBONIC DEVICE.

Application filed January 28, 1822. Serial No. 582,858.

and State of Connecticut, have invented certain newandusefulImprovements in Autoelectro'nio Devices, of which the following is aspecification.

The invention relates to an electron releasin device, embodying an autoelectronic efiect, that is to say a release of electrons due solely toan electric field, for .example, a device of the nature set forth in myco-pending U. S. application, Serial N 0. 364,215, filed the 8th day ofMarch, 1920. In this application there is disclosed a sealed envelope orvessel, evacuated to such a high degree that ionization is substantiallyabsent, said vessel enclosing also unheated electrodes separated by agap sufficiently short to permit the starting of a discharge ofelectrons between said cold electrodes upon the application of asuitable potential. The present invention, however, relates to a novelform of the electron releasing cathode, particularly as to its shape andthe metal comprising same, and to the method of producing such cathode.It has for its object in an autoelectronic device of this character, toprovide an autocathode.or member releasing electrons solely under theinfluence of an electric field and of such special design andcomposition as to admit of employing much lower voltages than haveheretofore been possible in the use of hi hly evacuated containers withcold electro e or electrodes. A very considerable reduction of thevoltage may be obtained by makin the cathode of an extremely fine wirean providing a superfine point on itnot b mechanical means, however, butby chemical action. I have found that by employin for the cathode suchmetals. as are founf at the most electro-positive end of the scale, asthe alkali metals and alkaline earth metals, the voltage necessary tocause current to pass between cold e ectrodes, in the absence of anysubstantial ionization and with predetermined gap, is greatly reduced.The degree of reduct1on appears to be eatest with the mostelectro-positive meta s-such as caesium, rubidium, otassium, sodium andlithium, while diminishing when approachthe alkaline earth metals.Moreover, an al- .loy of two or-more ofsa'id metals may be utilized forthe production of a cathode. For example, in working with caesium, anadmixture-of potassium, sodium or other metal of higher meltin point isuseful to make the caesium liar er and reduce the pressure of its vapor.

Moreover, the mere presence within the highly evacuated container of themetals set forth, as in causing same to be deposited 1n any part of thecontainer, has a beneficlal efiect for some of the metal eventuallyfinds its way to the cathode.

The invention contemplates, furthermore, a novel method for preparing anautocathode from these metals, which normally are not suitable forexposure to the atmosphere, in forming such cathode in the envelopeafter evacuating it to a high degree.

The nature of the invention, however, will best be understood whendescribed in connection with the accompanying drawings, in which- Fig. 1represents a glass envelope, designed to be highly evacuated andprovided with means for introducing metal.

Fi 2 and 3 illustrate similar vessels provided with diiferent means forintroducing the metal. 1

Similar characters of reference designate corresponding parts thruoutthe several views.

Referring to the drawings, 10 designates a glass envelope or vesselwhich is designed to be evacuated, thru a suitable outlet which issubseguently sealed, as is well understood. Anano e 11 and a cathode 12are provided in the vessel 10, to cooperate in manner set forth in myco-pending ap lication Serial No. 364,215, filed March 8t 1920; but inaccordance with the present invention, the cathode is a superfine pointand also comprises a metal such as is found at the most electro-positiveend-of the scale.

Referring more particularly to Fig. 1, in addition to the two electrodesnoted, there is further provided a pointed or sharp-edged blade member15 in proximity to the anode and a similar member 16 in proximity to thecathode, said members being designed to provide bombarding electrons fortheir re'- a spective electrodes to heat up same and free them fromoccluded gases in the evacuation of the vessel.

The cathode 12 has been shown as a fine wire, about one-tenth of amillimeter, with a superfine point, that is to say a point which under amagnification of several hundred diameters, still appears as a point. Inaccordance with the invention, this wire is to be coated with a metalsuch as is found at the most electro-positive end of the scale, forexample an alkali metal as caesium.

Such superfine points may be obtained of fine wire which has beenemployed as an anode in an electrolytic process, or has been dipped intoa suitable solvent until reduced to the necessary degree of fineness. Iftungsten be used to receive the cathode coating,

the tungsten wire may be dipped into poin proximity to the cathode.

tassium nitrite. In the case of a glass or quartz support for thecathode coating, fluoric acid may be used to point the glass. Othermeans for obtaining fine points of the wire consist in utilizing same asan electrode for a gas discharge, are discharge, spark discharge, etc. a

To effect the introduction of the cathode metal, which is subject toimmediate oxidation, into the vessel 10 and its deposition on thecathode 12, cathode metal 20, as caesium or for example another of themore volatile metals such as rubidium, potassium and sodium, or an alloythereof, is placed in the outermost bulb of a series of connected bulbs21. These bulbs terminate in the vessel 10 thru a tube 22 havin itsoutlet T e metal is successively distilled from one bulb to the next,while sealing off the last empty bulb so'that, finally, a metallicdeposit in a high state of purification and free of gases, Will beproduced within thevessel 10 and upon a portion of the cathode support12, forming a coating thereon of caesium or of another metal found atthe most electro-positive end of the scale and from which electrons maybe projected at much lower voltages than have been heretofore-possible.

Another means of introducing the cathode metalto form'the autoelectroniccathode is illustrated in Fig. 2. The metal '30, in this instance, as inthe former case is successively distilled thru a series of-bulbs 31 intoa tube 32 surrounding the cathode support 33 and deposited thereon toform a suitable coating. Or, when the character of the metal will permitofso' doing, itmay be melted andcaused to run down thru the tubeand-over the cathode support, subseuently cooling and forming a solidcoating.

t ereon. A further expedient is set forth in Fig. 3,

port passes. The cap member 36 is desi ed to retain a capsule or disk ofthe cat ode metal 37 and the member is then heated to volatilemetalssuchas calcium, strontium,

barium and lithium' and the heating is effected by means of bombardingelectrons discharged from an electrode 38 mounted in the vessel inproximity to the cap, said bombardment serving also to drive out anyoccluded gases therein. By this expedient, only a slight amount of thecathode metal condenses outside of the cathode point. This is a decidedadvantage as. the electronic discharge will then not find a metalliccoating from which gases would be set free thereby and affect the degreeof vacuum and consequently the electron releasing effect. In the use ofthe metals for cathodes as hereinbefore set forth, it has been possibleto reduce the voltage required to such an extent so that the devicebecomes suitable for use as a detector or transmitter ofelectro-magnetic waves and for amplification purposes.

I claim 1. An autoelectronic device, comprising a sealed envelopeevacuated to such a high degree that ionization is substantiallyprevented, and containing a metal found at the most electro-positive endof the scale, and un heated electrodes therein, separated by a gapsufficiently short to permit of starting the discharge therebetween uponthe application of a suitable potential.

2. An autoelectronic device, comprising a sealed envelope evacuated tosuch a high degree that ionization is substantially prevented, andunheated electrodes therein, one of which comprises a metal found at themost electroositive end of the scale, said electrodes being separated bya gap sufiiciently short to permit of starting the dischargetherebetween upon the application of a suitable potential. v

3. An autoelectronic device, comprising a sealed envelope evacuatedto'such a high degree that ionization is substantially prevented, andunheated electrodes therein, one of which consists of an alkali metal,said electrodes being separated by a gap sufliciently short to permit ofstarting the discharge therebetween upon the application of a suitablepotential.

4. An autoelectronic device, comprising a sealed envelope evacuated tosuch a high degree that ionization is substantially pre vented,- andunheated electrodes therein, one of which comprises caesium, saidelectrodes being separated by a gap sufficiently short to permit of thedischarge therebetween upon the application of a suitable. potential. 5.n autoelectroni'c device, comprising a sealed envelope evacuated to sucha. high degree that ionization is substantially prevented, and unheatedelectrodes therein, one.

' of-which consists of a support coated with caesium,- said-electrodesbeing separated by; ,a gap sufliciently short to permit of startingseparated by a gap 'sufliciently short to 'permit of starting thedischarge therebetween upon the application of a suitable potential.

7. An autoelectronic device, comprising a sealed envelope evacuated tosuch a high degree that ionization is substantially prevented, andunheated'electrodes therein, one of which consists of a superfinesupport coated with a metal found at the most electro-positive end ofthe scale, said electrodes being separated by a gap sufliciently shortto permit of starting the discharge therebetween upon the application ofa suitable potential.

8. Anautoelectronic device, comprising a sealed envelo evacuated to sucha high degree that ionization is substantially prevented, and unheatedelectrodes therein, one of which consists of a superfine support coawith caesium, said electrodes being separated by a gap suflicientlyshort to permit of starting the discharge therebetween upon theapplication of a suitable potential.

9. An autoelectronic device, comprisin a sealed envelope evacuated tosuch a high egree that ionization is substantially prevented, andunheated electrodes therein, one of which consists of a superfinesupport "coated with an alloy of'ceesium-and potassium, said electrodesbeing separated by a gap sufliciently short to permit of starting thedischarge therebetween upon the application of a suitable potential.

10. An autoelectronic device, comprisin a sealed envelope evacuated tosuch a'hig degree that ionization is substantially pre vented, andunheated electrodes therein, one of which consists of a superfine.support coated with an alloy. of caesium, potassium and sodium, saidelectrodes being separated by a ap sutficiently short to permit ofstarting the discharge therebetween upon the apphcation of a suitablepotential.

Signed at Waterbury, in the county of New Haven and State ofConnecticut, this 26th day of January, A. D. 1922,

JULIUS EDGAR LILIENFELD.

